In an ecosystem where most flowers are long and bell-shaped, the hummingbirds with longer beaks would have a better adaptation for accessing the nectar in those flowers. This would likely provide them with a greater feeding advantage compared to the short-beaked hummingbirds. Over time, due to natural selection, the population would likely consist of more long-beaked hummingbirds, as they would be more successful in feeding and reproducing in this environment.
Therefore, the most likely hummingbird population composition is:
more long-beaked hummingbirds.